What is the treatment of arsenic-containing waste residue containing arsenic fume?

　　China is rich in arsenic resources, with proven reserves accounting for about 70% of the world's total reserves. Arsenic is a non-essential element for human body, but arsenic and arsenic-containing compounds are harmful to human health and very toxic. So, what are the arsenic-containing waste residues of arsenic-containing soot treatment?

　　What is the treatment of arsenic-containing waste residue containing arsenic fume?

　　1, fire method: treatment of arsenic-containing waste slag is a traditional method. Oxidation roasting, reduction roasting or vacuum roasting of high arsenic waste residue to obtain crude white arsenic products. Or after further oxidation roasting at 600~850, 40%~70% of arsenic in the waste slag will be volatilized. The addition of vulcanizing agent during roasting can increase the arsenic volatilization rate to 90%~90%. If the arsenic-containing waste slag after grinding is roasted under moderate vacuum, the arsenic removal rate can reach 98%. The process has the advantage of large processing capacity, especially suitable for processing materials with arsenic content greater than 10% in the slag, but there are also disadvantages such as difficult to control the working environment, easy to cause environmental pollution, low product recovery rate, poor product quality, high investment costs, and small range of raw materials.

　　2、Sulfuric acid leaching method: Acid leaching method is to treat arsenic-containing waste slag with sulfuric acid in a closed reactor. This method has the advantage of not producing arsenic and other toxic gases, less waste water, the disadvantage is the high equipment requirements, high cost. The arsenic-containing waste slag is treated with sulfuric acid (80%) at a liquid-solid ratio of 6:1, 180, with a reaction of 2~3 h. The mother liquor will be separated from elemental sulfur by liquid-solid separation. Then the mother liquor will be cooled and crystallized to get arsenic sulfide slag for process treatment. The leaching will be accelerated by pressurization with industrial oxygen, and the number of liquid-solid separation is less. Under the conditions of H2SO concentration of 21.5%, temperature of 150, oxygen pressure of 0.55 MPa and reaction time of 5 h, the leaching rate of arsenic from the slag was 97.68%.

　　3、Copper sulfate replacement method: The arsenic-containing waste slag from industrial waste acid and wastewater treatment mainly includes arsenic sulfide slag, iron acid and calcium acid slag. Arsenic in the arsenic sulfide slag can be replaced with copper sulfate solution copper leaching, and then oxidized with a blast and strong stirring. Then treat H3AsO with 7%~8% SO as reducing agent. is a mature method to treat arsenic-containing slag. No secondary pollution, but there are defects such as complex process flow, high copper consumption, high production cost, long operation time of replacement oxidation process, leaching slag, and low comprehensive utilization. This method can be used to separate the arsenic from other heavy metal ions, the purity of arsenic can reach more than 99%.

　　4, iron sulfate method: iron sulfate method is to leach arsenic sulfide with iron sulfate solution under high pressure, so that different metal elements are separated from the slag. Since this method must meet the high-pressure conditions, it brings the disadvantages of complex production equipment and high cost. Compared with other wet processes, the iron sulfate process not only makes the arsenic-containing soot harmless, but also makes comprehensive use of valuable components such as bismuth and white arsenic, and the degree of comprehensive utilization of waste residue and environmental benefits are superior. However, this method also has some drawbacks, such as more return material, complex process flow, more cooling equipment, large investment, etc. The average content of arsenic in the leaching solution is 0.05%. The excellent process conditions for iron precipitation were: temperature 90,pH 3.54 and time 90 min. All valuable components in the slag of this process could be effectively recovered, with obvious environmental and economic benefits.